Breaking the Size Limitation of Directly-Synthesized PbS Quantum Dot Inks Toward Efficient Short-wavelength Infrared Optoelectronic Applications.

PbS quantum dots (QDs) are promising building blocks for solution-processed short-wavelength infrared (SWIR) devices. The recently developed direct synthesis of semi-conductive PbS QD inks has substantially simplified the preparation processing and reduced the material cost, while facing the challenge to synthesize large-size QDs with absorption covering the SWIR region. Herein, we for the first time realize a low-cost, scalable synthesis of SWIR PbS QD inks after an extensive investigation of the reaction kinetics. Finally, based on these PbS SWIR QD inks, the solar cell demonstrates a record-high power conversion efficiency (PCE) of 1.44 % through an 1100 nm cutoff silicon filter and the photodetector device shows a low dark current density of 2×10-6  A cm-2 at -0.8 V reverse bias with a high external quantum efficiency (EQE) of 70 % at ≈1300 nm. Our results realize the direct synthesis of low-cost and scalable SWIR QD inks and may accelerate the industrialization of consumer SWIR technologies.

Merging Passivation in Synthesis Enabling the Lowest Open-Circuit Voltage Loss for PbS Quantum Dot Solar Cells.

The high open-circuit voltage (Voc ) loss arising from insufficient surface passivation is the main factor that limits the efficiency of current lead sulfide colloidal quantum dots (PbS CQDs) solar cell. Here, synergistic passivation is performed in the direct synthesis of conductive PbS CQD inks by introducing multifunctional ligands to well coordinate the complicated CQDs surface with the thermodynamically optimal configuration. The improved passivation effect is intactly delivered to the final photovoltaic device, leading to an order lower surface trap density and beneficial doping behavior compared to the control sample. The obtained CQD inks show the highest photoluminescence quantum yield (PLQY) of 24% for all photovoltaic PbS CQD inks, which is more than twice the reported average PLQY value of ≈10%. As a result, a high Voc of 0.71 V and power conversion efficiency (PCE) of 13.3% is achieved, which results in the lowest Voc loss (0.35 eV) for the reported PbS CQD solar cells with PCE >10%, comparable to that of perovskite solar cells. This work provides valuable insights into the future CQDs passivation strategies and also demonstrates the great potential for the direct-synthesis protocol of PbS CQDs.

Open-Shell Diradical-Sensitized Electron Transport Layer for High-Performance Colloidal Quantum Dot Solar Cells.

The zinc oxide (ZnO) nanoparticles (NPs) are well-documented as an excellent electron transport layer (ETL) in optoelectronic devices. However, the intrinsic surface flaw of the ZnO NPs can easily result in serious surface recombination of carriers. Exploring effective passivation methods of ZnO NPs is essential to maximize the device's performance. Herein, a hybrid strategy is explored for the first time to improve the quality of ZnO ETL by incorporating stable organic open-shell donor-acceptor type diradicaloids. The high electron-donating feature of the diradical molecules can efficiently passivate the deep-level trap states and improve the conductivity of ZnO NP film. The unique advantage of the radical strategy is that its passivation effectiveness is highly correlated with the electron-donating ability of radical molecules, which can be precisely controlled by the rational design of molecular chemical structures. The well-passivated ZnO ETL is applied in lead sulfide (PbS) colloidal quantum dot solar cells, delivering a power conversion efficiency of 13.54%. More importantly, as a proof-of-concept study, this work will inspire the exploration of general strategies using radical molecules to construct high-efficiency solution-processed optoelectronic devices.

Microwave pretreatment power and duration time effects on the catalytic pyrolysis behaviors and kinetics of water hyacinth.

In this work, the power and duration time of microwave pretreatment effects on water hyacinth were the main research objects. Surface structure of water hyacinth was broke by microwave radiation through Scanning Electron Microscope observation and the characteristics of thermal decomposition of water hyacinth with the catalyst under four heating rates was investigated by using the thermogravimetric analyzer. Calcium oxide was chosen to be the additive of the water hyacinth pyrolysis reaction. Pyrolysis product compositions were figured out by Pyrolysis-Gas Chromatography/Mass Spectrometry. The results showed that microwave changed the product composition effectively. Under optimal conditions, acids yield of water hyacinth decreased from 7.89% to 4.89% and the yield of sugars increased from 2.73% to 9.04%. Kinetic parameters were calculated by Flynn-Wall-Ozawa method. Under microwave pretreatment at 329 W and 567 W, the activation energy of water hyacinth first decreased and then rose with duration time increasing.

General distributed activation energy model (G-DAEM) on co-pyrolysis kinetics of bagasse and sewage sludge.

In this work, pyrolysis kinetic evolution of mixture of bagasse and sewage sludge with 10%, 30% and 50% (respect to dry initial weight). In terms of kinetic mechanism, the uncertainty of the activation energy obtained by mode-free method was barely known. We found that increasing number of heating rates made result more reliable, but the modeling process more dependent on redundant experiments with extra data. We adapted a novel general distributed activation energy model (G-DAEM) with 5 pseudocomponents for the analysis of kinetic evolution with proposing a more applicable approximation to the general temperature integral. The G-DAEM was trained by data for 20 K/min, and the predictions were performed on data for 15 K/min and 25 K/min. The predictions were well matched to the experimental data. The G-DAEM enhances modeling efficiency of kinetics and provides a effective pathway for high precise model of complicated co-pyrolysis process.

Co-pyrolysis kinetics of sewage sludge and bagasse using multiple normal distributed activation energy model (M-DAEM).

In this study, the kinetic models of bagasse, sewage sludge and their mixture were established by the multiple normal distributed activation energy model. Blending with sewage sludge, the initial temperature declined from 437 K to 418 K. The pyrolytic species could be divided into five categories, including analogous hemicelluloses I, hemicelluloses II, cellulose, lignin and bio-char. In these species, the average activation energies and the deviations situated at reasonable ranges of 166.4673-323.7261 kJ/mol and 0.1063-35.2973 kJ/mol, respectively, which were conformed to the references. The kinetic models were well matched to experimental data, and the R2 were greater than 99.999%y. In the local sensitivity analysis, the distributed average activation energy had stronger effect on the robustness than other kinetic parameters. And the content of pyrolytic species determined which series of kinetic parameters were more important.

A study on microwave-assisted fast co-pyrolysis of chlorella and tire in the N2 and CO2 atmospheres.

The microwave-assisted fast co-pyrolysis of chlorella and tire with additive under N2 and CO2 atmospheres were investigated. The pyrolysis profiles, yields of three-phase, the chemical composition of liquid and the ultimate analyses of solid residues were gained. With the tire ratio increasing, all the characters had the changes. The finial temperature had a wave change. The yield of liquid decreased and the chemical composition obtained in liquid of oxygenates compounds decreased, while hydrocarbon compounds increased, among which aromatic hydrocarbons had the highest content. The yield of solid increased, the HHV had a wave change and the values of H/C decreased. Under CO2 atmosphere, the final temperatures were lower with 70% and 100% chlorella ratios, the yield difference of liquid reached the minimal with 70% and 30% chlorella ratios. According to the quantity and quality of liquid and solid, and the former results, 50% percentage of tire was the suitable ratio.

Ultrasonic pretreatment effects on the co-pyrolysis of municipal solid waste and paper sludge through orthogonal test.

In this study, the influences of ultrasonic pretreatment factors (frequency, power, treatment time) on blends of municipal solid waste (MSW) and paper sludge (PS) with additive (MgO) was explored, through orthogonal experiments design. The optimum operating condition wanted to be acquired. However, for the ultimate (H/C) and ash analysis after pretreatment, solid residue mass and oxygenates compounds contents in products, the influences of factors were in different results. With adding PS unceasingly, the contents of hydrocarbon compounds decreased. And the ultrasonic pretreatment had the obvious influence with high PS percentage. Longer treatment time resulted to the lower content of oxygenates compounds. After adding MgO, the residue mass reduced, which meant MgO had the catalytic action, and the oxygenates compounds content reduced only with 100 kHz, which had the sonochemical effect.

Effects of additives on the co-pyrolysis of municipal solid waste and paper sludge by using thermogravimetric analysis.

By using thermogravimetric analysis (TGA), the effects of different additives (MgO, Al2O3 and ZnO) on the pyrolysis characteristics and activation energy of municipal solid waste (MSW), paper sludge (PS) and their blends in N2 atmosphere had been investigated in this study. The experiments resulted that these additives were effective in reducing the initial temperature and activation energy. However, not all the additives were beneficial to reduce the residue mass and enhance the index D. For the different ratios of MSW and PS, the same additive even had the different influences. The catalytic effects of additives were not obvious and the pyrolysis became difficult with the increase of the proportion of PS. Based on all the contrast of the pyrolysis characteristics, MgO was the best additive and 70M30P was the best ratio, respectively.

[Role and significance of pelvic four-contrast defecography in the diagnosis of outlet obstructive constipation].

OBJECTIVE: To study the changes in pelvic floor morphology and relationships of the pelvic organs in patients with outlet obstructive constipation (OOC). METHODS: Fifty-nine OOC patients and 12 healthy volunteers were examined by simultaneous pelvic four-contrast defecography, including pelvicography, vaginal opacification, voiding cystography and defecography. The levels of perineum, peritoneum and bladder, and anorectal angle were measured and recorded. RESULTS: Among the 59 OOC patients, 46 cases of internal rectal prolapse (IRP), 29 cases of pelvic floor hernia, 7 cases of rectocele (RC), 7 cases of spastic pelvic floor syndrome (SPFS), 5 cases of descending perineum syndrome were diagnosed by pelvic four-contrast defecography. Six cystoceles and 10 uterine prolapses were also found by pelvic four-contrast defecography. Compared with healthy volunteers, OOC patients had significantly large anorectal angles during defecation (P<0.05), abnormality descending of perineum during rest and defecation (P<0.05, P<0.01), and a deep pouch of Douglas during defecation (P<0.01). OOC patients combined with urinary system symptoms had an abnormal descent of the bladder during rest and defecation (P<0.05, P<0.01). CONCLUSION: Pelvic four-contrast defecography is an effective method for the diagnosis of IRP, RC, pelvic floor hernia, peritoneocele, cystocele and uterine prolapse, and is helpful in the selection of proper surgical procedures for the treatment of OOC.

Role of pelvicography and colpocystodefecography in diagnosis of outlet obstructive constipation.

AIMS: The aim was to research the changes in pelvic floor morphology and corresponding visceras in patients with outlet obstructive constipation (OOC). PATIENTS AND METHODS: Thirty-eight patients with OOC and 12 healthy volunteers were enrolled in this study. With simultaneous pelvicography and colpocystodefecography (PCCD), including pelvicography, vaginal opacification, voiding cystography and defecography, pelvic floor morphology was observed and the anorectal angle, the level of the perineum, peritoneum and bladder were measured. RESULTS: Thirty-seven cases of internal rectal prolapse (IRP), 5 cases of rectocele (RC) and 5 cases of spastic pelvic floor syndrome SPFS were diagnosed by PCCD. 12 IRP, 4 RC and 1 SPFS were detected by common physical examination. All of these were confirmed by PCCD. Moreover, PCCD found 9 pelvic floor hernia or peritoneoceles, 6 cystoceles, 3 descending perineum syndromes and 10 uterine prolapses. Compared with controls, OOC patients had a significantly large anorectal angle during defecation, abnormal descending of the perineum at rest and during defecation, and a deep pouch of Douglas during defecation. Some patients with urinary system symptoms may have had an abnormal descent of the bladder during rest and defecation. CONCLUSION: Simultaneous PCCD has a higher positive ratio than the common physical examination in diagnosing IRP and RC, and provides information for the diagnosis of pelvic floor hernia or peritoneocele, cystocele or uterine prolapse. PCCD is helpful in the selection of a proper surgical procedure.